P0128 Fault on 2004 Toyota Sienna at 140K Miles - Should I Repair or Continue Driving?
I'm experiencing a P0128 diagnostic trouble code on my 2004 Toyota Sienna, which has accumulated 140,000 miles. The vehicle has been running smoothly despite the code appearing for the past two months. The check engine light typically turns off during warm weather or when the air conditioning is running—likely due to the engine warming up sufficiently—but returns within a day or two. I live in San Jose, where winter temperatures are mild, so an open thermostat is unlikely to be the primary issue. Given that the car is already well past its expected lifespan and used only for short trips, I'm wondering whether it's worth investing more money to fix the P0128 code. Should I proceed with repairs or continue driving it for another year or so? Any expert advice would be greatly appreciated.
I recommend addressing the issue. An engine that operates cooler than designed can lead to reduced fuel efficiency and fuel puddling in the intake manifold, which over time may damage the catalytic converter. While the current symptoms are not severe, long-term exposure to a cold-running engine could compromise emissions performance and overall engine health.